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Bridging the Worlds of Art and Science

Home to the tomb of St. Wenceslas, who's legacy lives on in the popular Christmas carol, "Good King Wenceslas," St. Vitus Cathedral hosts a variety of the Czech Republic's cultural treasures. Czech royalty arrived at the French Gothic structure for their coronations. Today, the medieval church continues to attract worshippers for religious services.

The Last Judgment mosaic adorns the southern entrance to the cathedral. The masterpiece stretches across 904 square feet. No information is available about who actually made the mosaic or where the mosaic tiles originated.

Work among the Getty Conservation Institute, the University of California, and California State University began in 1992 to develop a long-term solution for the decaying mosaic. The project set out to clean the corroding glass and to understand what caused the corrosion.

Nearly 100 samples of varied colors were analyzed using Neutron Activation Analysis. This process involved grinding the small samples of the glass into powder and exposing them to neutron bombardment radiation in the TRIGA nuclear reactor at the University of California Irvine.

The study detected 25 elements in the mosaic samples. Scientists determined that unlike Italian glass, the glass in the Last Judgment is potassium based. This is typical of Central European glassmaking of the period. This high potassium level is an important reason for the extensive corrosion problem.

Neutron activation can also detect elements at extremely low concentrations and have much greater sensitivity than non-nuclear methods. This process also allows researchers to identify the material much faster and for much less expense than with non-nuclear technologies.